Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing the new design.

Within the drawings, the outermost broken lines illustrate the displayscreen or portion thereof and form no part of the claimed design. Theremaining broken lines illustrate portions of the graphical userinterface and form no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.